N.times.N couplers are used extensively in the optical communications industry to route light beams in fiber optic Local Area Networks (LAN). They are used also in fiber optic sensor systems to replace bulk optic components such as beam splitters.
N.times.N couplers are commercially available for some types of optical fibers, such as glass fibers, but not for some other types, such as plastic fibers and plastic clad silica fibers.
The main reason that N.times.N coupler devices are not currently available for some kinds of fibers is related to the present methods of fabrication. In typical present methodology, N fibers are grouped together, heated, pulled, and twisted to "fuse" the fiber cores together. The "fused couplers" are the industry standard. Most glass fibers and some plastic fibers are amenable to being used to form fused couplers, but other types are not. Because each splitter is individually fabricated using the twist and pull techniques, the products are expensive and have large variations in splitting characteristics.
The present invention comprises novel methods of fabricating couplers without using the fusing technology. Instead, fibers typically are attached to a photofabricated waveguide which divides and/or combines the light as desired. Hence, this invention provides N.times.N couplers of types that were not previously available. Further, it can produce multiple copies of couplers simultaneously, which reduces overall cost. Also, the technique can be custom designed to match the properties of a variety of fiber materials of different sizes and numerical apertures.